Head-lice shampoos can be dangerous

September 2003

ConsumerReports.org

The millions of kids who will inevitably turn up with head
lice during the coming school year have gained Food and Drug Administration protection against one dangerous prescription treatment--lindane, an organochlorine insecticide that can be toxic to brain cells. But another prescription lice shampoo--brand-named Ovide--is being marketed with use instructions that increase the risk of harm.

The FDA recently recommended that lindane be used only with extreme caution in anyone weighing less than 110 pounds, which includes most school-aged children. Consumers Union, publisher of Consumer Reports, has long advocated taking lindane off the market.

The makers of Ovide, which has been available in the U.S. since 1999, have moved to take over lindane’s market share. Ovide’s active ingredient is malathion, an insecticide whose use for mosquito control has alarmed parents across the U.S.

Though it’s one of the safer organophosphate insecticides--considerably safer than lindane--malathion works by interfering with chemical reactions in the nervous system, whether of an insect or a person. In its raw state, malathion readily soaks through the skin. So far, the makers of Ovide have not done studies to determine how much of the malathion gets into a child’s circulatory system.

That said, years of use have established that when applied to the scalp for lice control, Ovide is not absorbed excessively. But lice experts say that the product’s use instructions pose an unnecessary hazard.

A recent study by Terri Meinking, associate professor of dermatology at the University of Miami School of Medicine, found that “Ovide killed lice within 20 minutes of exposure, by far the fastest of any product tested.” However, the product’s instructions say to soak the child’s hair with Ovide and leave it on for 8 to 12 hours. The longer it stays on the head, the more of it is absorbed--and the more likely that lice will quickly become resistant to it. Moreover, it smells bad and might catch fire if the child is near a flame.

If your child gets head lice, remember that though they are unpleasant, lice neither transmit disease nor make children ill. “The major hazard of head lice is enforced school absence” because of draconian “no-nit” policies, says Ronald C. Hansen, M.D., chief of pediatric dermatology at Phoenix Children’s Hospital in Arizona. If your child’s school has such a policy, refer its administrators to the American Academy of Pediatrics, whose guidelines explicitly discourage it.

Many lice cases can be resolved by starting with over-the-counter treatments, such as Nix or Rid, which contain relatively safe pyrethroid insecticides. Carefully follow package instructions. Check the child’s head daily, and remove remaining lice and nits with a fine-tooth metal comb until you have gone several days without spotting any. Wetting the child’s hair with a conditioner may make combing less painful. Use Ovide as a last resort, leaving it on for only 10 to 15 minutes, then washing the child’s hair to remove all residue.